The present invention relates to float valves of the type commonly used in hydrocarbon recovery operations when conducting cementing operations. More particularly, the present invention relates to an improved float valve which may be reliably secured inside a tubular irrespective of the type of threads on the end of the tubular casing grade, and casing weight. This invention includes an improved method of reliably securing the float valve inside a tubular.
Those familiar with hydrocarbon recovery operations appreciate the importance of reliably cementing the well casing within the hole. It is thus common practice within the cementing operations to install one or more float valves in the lower portion of the casing string. These float valves may be in the form of a float shoe or a float collar, and typically consist of a float valve housed within a steel casing which in turn becomes an integral portion of the casing string, i.e., the float valve housing is threaded between two joints of casing. The float valve is preferably fixed into the steel housing with a special blend of cement which subsequently facilitates drilling out the float valve.
Float shoes and float collars are thus commonly stocked by service companies in popular casing sizes, weights, and casing threads, which are conventionally either API 8-round or Buttress. A partially composite material or plastic material float valve body according to the prior art was thus conventionally secured to the steel housing with threads at both ends of the steel housing, with the float valve body being secured by a cement liner provided when the poured cement is cured to secure the float valve body to the steel housing. When the customer, typically an oil company, elects to use well casing that employs a non-API casing thread, special pieces of floating equipment may have to be custom built to match the casing size, weight, grade, and thread profile. In addition, if a stage cementing job is to be performed, additional float equipment commonly in the form of a baffle adapter must be supplied which is compatible with the particular casing string being used. These requirements interject significant expense in the cost of the well program and require pre-planning on the part of both the customer and the vendor of the float equipment to insure that the required equipment will be available when needed.
Prior art float valves are disclosed in U.S. Pat. Nos. 3,997,009 and 5,379,835. The Baker Line Model F Drill Pipe Float Valve is disclosed in Technical Manual Number 480-13. Valves and sealing assemblies commonly used in cementing operations are disclosed in U.S. Pat. Nos. 4,624,316 and 5,450,903.
The disadvantages of the prior art are overcome by the present invention. An improved float valve and technique for securing the float valve within the interior of a casing string is hereinafter disclosed. The float valve and technique of the present invention provide a universal float valve which may be used on a particular range of casing sizes and weights without regard to the casing thread type and pipe grade. The present invention provides a float valve with improved drill-out capability, high reliability, and reduced equipment inventory and rig-time costs compared to prior art equipment and techniques. The disadvantages of the prior art are thus overcome by the invention as described subsequently.
In a preferred embodiment, the basic components of the system include a modified composite packer, a plug seat, a float valve, and an optional guide nose. According to the method of the present invention, the drillable composite packer may be inserted into a joint of casing at the surface and then set utilizing a hydraulic setting tool. Once set, the setting mandrel and upper shoe may be retrieved from the joint of the casing, and the cannister type float valve then inserted into the receiving cavity of the body of the set packer. The float valve may be retained within the set packer by various conventional mechanisms including glue, a lock-ring, or threads. A hydraulic seal between the float valve body and the set packer may be effected by a glue joint and/or elastomeric seals. If the tool is to be used as a float shoe, a suitable composite nose piece with a desired shoe profile may be inserted into the pin end of the casing.
It is an object of the present invention to provide an improved float valve and a method of securing the float valve within a casing joint, wherein the float valve body may be reliably secured within a casing joint within manageable variations in the internal bore diameter of the casing joint, but also without regard to the threads at the ends of the casing joint being used. It is another object of the present invention to provide improved method of securing a float valve within a casing joint at the surface. The method offers the benefits of saving valuable rig time. The present invention may also eliminate the need to fixedly cement the float valve within the casing string.
Yet another object of the invention is to provide an improved float valve which is easily drillable after the cementing operation, utilizing a conventional PDC drill bit. It is a further object of the present invention to provide a float valve which may be used as either a float collar or a float shoe (with the addition of a nose profile), depending upon the desires of the operator.
It is an object of the present invention to provide an improved tool which replaces both conventional and specialized floating equipment and baffle adapter pieces. A single tool according to the invention is compatible for use in a range of oilfield casing sizes, irrespective of the weight, grade, or casing thread within the permissible size range of the given tool.
It is a feature of the invention that the universal aspects of this float valve significantly reduce inventory and the need to maintain stocks of equipment and drawings to support the myriad of possible casing threads, casing grades and weights, and combinations for each of the various casing sizes.
It is a further feature of the present invention that the components of the float valve preferably are formed of composite materials and little if any aluminum components are used, thereby enhancing the drillability of the float valve.
It is a further feature of the invention that the float valve has enhanced reliability by utilizing proven packer technology and reducing concerns about float body cement fracturing due to over-pressure.
It is a further feature that the method of the present invention streamlines manufacturing operations by eliminating the need to pour float body cement and maintain quality control on the cement product.
A significant advantage of the present invention is the high cost savings attained by using universal downhole equipment rather than equipment which inherently must be configured to threadably mate with the threads of the various weights and thread profiles of the different casing strings.
These and further objects, features, and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.